제주지역 대기 라돈과 오염물질의 시계열 변화 및 기류 유입경로별 농도 비교

Abstract

The concentrations of atmospheric radon-222 and gaseous pollutants were measured at the Gosan site in Jeju Island for 2010∼2017, in order to observe their time-series variation characteristics and examine the concentration changes related to the airflow transport pathways. The mean concentration of radon for the period was 2,392 mBq m-3, and the annual mean concentrations were in the range of 2,178～2,555 mBq m-3. In seasonal comparison, the order of the seasonal mean concentrations was as fall (2,892 mBq m-3) > winter (2,839 mBq m-3) > spring (2,192 mBq m-3)> summer (1,831 mBq m-3). The monthly mean concentrations were in the order of Nov > Oct > Jan > Dec > Feb > Sep > Mar > Jun > May > Apr > Aug > Jul, resulting that the highest concentration (3,012 mBq m-3) on November was over twice as the lowest (1,458 mBq m-3) on July. The diurnal variation of radon showed the highest concentration (2,741 mBq m-3) was at around 7 a.m. and the lowest (1,989 mBq m-3) at around 3 p.m., revealing the higher concentration increase during nighttime. Based on the realtime monitoring of gaseous pollutants during 2010-2015, the hourly mean concentrations of SO2, CO, O3, and NOX were 1.3, 377.6, 41.1, and 3.9 ppb, respectively. On monthly variations of the gaseous pollutants, the mean concentrations of SO2, CO, and NOX were the highest in January and the lowest in July. Some gaseous pollutants (SO2, CO, NOX) showed a similar seasonal variation with radon concentration as high in winter and low in summer, whereas the O3 concentrations had a bit different seasonal trend. According to the clustered back trajectory analyses, the frequencies of airflow pathways moving from continental North China, East China, Japan and the East Sea, Korean Peninsula, and North Pacific Ocean routes were 36, 37, 10, 13, and 4%, respectively. When the airflow were transported to Jeju Island from continental China, the concentrations of radon and gaseous pollutants were relatively high. On the other hand, when the airflows were transported from North Pacific Ocean and East Sea, their concentrations were much lower than those from continental China. In comparison by wind direction, the concentrations of radon, SO2, O3, CO, and major ions in PM10 and PM2 were relatively high when the wind blows from the northwest direction (225°-351°, China continent), showing a similar pattern of radon with other air pollutants.